it's a model T key, the key is characterized by a head that is diamond shaped. While it was adopted on Feb. 21, 1919, the records suggest that this key was not used until after April 23. These keys were made out of nickel silver and the heads were “pin frosted” on both sides. A smooth 1/8” by 3/8” surface was provided on the back side of the key for the serial number of the key.These numbers ran from 51 to 74 inclusive and were used 1919-1927, so your key would be for any Ford with a #58 lock during those years. The front face bore the word “Ford” in script.
Bill